The invention describes a casing cover for an internal-combustion engine, particularly valve covers or oil pans, to be mounted detachably and fluid-tight to an engine block, with an elastomer seal at the edge of the casing cover,
Within the scope of complex assembly strategies in the automobile industry, it is the current practice to provide engine parts with features that facilitate assembly or allow joining devices to he eliminated altogether. In addition to these assembly aids, characteristics that influence the function of the components are integrated into the engine components.
The components addressed in particular here are casing covers, such as valve covers or oil pans, which are completely assembled when incorporated into the engine. As detachable, fluid-tight engine parts, such casing covers must possess numerous features while fulfilling specific capacities.
To produce a detachable connection, casing covers must be easy to mount and position, on the one hand, and comprise as few individual parts as possible, on the other hand.
The seal in a casing cover must possess specific properties including consistent shape, i.e., little relaxation, the ability to be reused many times, and a high resistance to fluids in the engine and environmental influences.
To counteract seal relaxation, European Patent Application No. EP 0 664 388 A1 proposes a generic casing cover as a valve cover for a cylinder head of an internal-combustion engine, in which the use of a metallic spring body allows the prestressing force on the seal to be adjusted. In this case, the seal at the cover edge is pressed against the engine block under a certain force during tightening. Through the use of the metallic spring body, the valve cover is in a position to follow the relaxation of the seal.
A drawback of this type of casing-cover design is that, while the force on the seal can be maintained at a relatively constant level, there is no countermeasure for a shifting movement of the cover edges over the sealing surface. Shifting movements of the cover edge may result from, for example, fatigue of the casing-cover material or excessive tightening moments of the cover screws. This is particularly the case when the casing-cover materials are insufficiently stable, the components cannot be constructed to be adequately rigid, or the screw arrangement is unfavorable. Moreover, the seal may be damaged by the shifting movement, or the sealing forces on the elastomer seal material may no longer suffice to prevent leaks.